Carrier current control system for electronic flash units



1964 M. A. MICHALSKI 3,119,047

CARRIER CURRENT CONTROL SYSTEM FOR ELECTRONIC FLASH UNITS Filed July 25,1960 MgsYZ/L IAN/4. Mama/r1 ORNEY United States Patent 3,119,647CARREIER CURE-RENT C(lNlRQL SYSTEM FUR I a ELECTRQNKC MASH UNITSMausyrnihan A. Michalski, Woodside, NFL, assignor to American SpeedlightCorporation, Middle Village,

Filed .luly 25', 19MB, Ser, No. 45,194 4- Claims. (Cl. 315-177) Thepresent invention relates to electric systems and more particularly to acarrier current control system for triggerin g electronic flash units.

in the use of electronic flash units for photographic illumination, itis often desirable to place the flash units at positions remote from thecamera. Such units have been heretofore triggered by phototubesresponsive to a flash at the camera, or connected by the use of synccords. it has been found that the wiring for the sync cords has beencumbersome and time consuming to position. The phototubes have notoperated satisfactorily when remotely positioned from the main flashbecause of the low light level. [also persons or objects have blockedthe transmission of light to the phototubes. Further, the operation ofthe phototubes has not been wholly satisfactory as they become aged.

in order to overcome these difficulties radio frequency control has beenused. However, because of static and other interference, and because ofthe governmental rcstrictions on use of radio equipment such equipmenthas not been used to any great extent.

The present invention aims to overcome the foregoing drfliculties anddisadvantages by providing a carrier current control system for theremote units and in which a carrier current signal is continuouslytransmitted, the transmitted signal being interrupted when the camerashutter is operated causing the receiver to generate a pulse whichtriggers the sla e flash unit. If desired a plurality of receivers maybe operated from a single transmitter.

The system in accordance with the invention is advantageous in that thereceivers may be selective as to transmitted frequency so that severaltransmitters may be operated at the same time without causinginterference with their respective receivers.

Another object of the invention is to provide a carrier current controlsystem for triggering electronic flash units which is simple andeconomical in manufacture efiicient in operation, rugged in use, and notsubject to actuation by static or iike interference.

Other objects and advantages of the invention will be apparent from thefollowing description and from the accompanying drawing which shows, byway of example, an embodiment of the invention.

in the drawings:

FEGURE l is a diagrammatic view of a transmitter in accordance with theinvention.

FIGURE 2 is a diagrammatic View of a receiver coupled to a flash unit inaccordance with the invention.

Referring to the drawings there is shown in FIGURE 1 a carrier currenttransmitting system in accordance with the invention and adapted to beconnected to a 120 volt alternating current supply line or the like. Thetransmitter includes a tube Frill, a transmitter coil 11 connected in anL-C circuit with tie tube ill. The transmitter coil 11 has a tankwinding 1?. and a tickler coil 13, an output coil 14 and a shortingwinding 15. The tube Ill) may be a power pentode or a triode connectedas a triode oscillator. A power supply is provided by a silicon orselenium rectifier 16 connected to grid 17 and to anode 18 of the tubeCathode i9 is connected to tap 2i) of the coil 12. Grid 21 of the tubelb has a grid leak bias formed by a capacitor 22 in parallel with aresistor 23 connected to end 24 of the tank winding 12. A paddercondenser Z hllihh l? ice is connected across the tank winding 12 andtickler coil 13 from terminal 24 to terminal 26. Heater filament 27 isconnected across the source of supply through a capacitor 28 to drop thesupply voltage, a filter capacitor 29 being connected from the filament27 to the grid 17. The shorting winding 15 is connected through'arectifier 30 to a switch 31 which may be actuated by the shutter of thecamera. Output coil 14 is coupled to the supply line by connecting itsterminal 32 through a capacitor 33 while its other terminal 34 isconnected to end 26 of the ticlder coil. If desired a neon lamp 4i maybe connected in series with a resistor 41 across the supply line after aswitch 43 and fuse 44 to indicate energization of the circuit.

In the operation of the transmitter a high frequency CW signal of afrequency of about 195 kilocycles plus or minus 46 kilocycles isadjusted to the desired frequency by varying the padder condenser 25.immediately upon energization of the circuit a carrier current istransmitted over the 120 volt power supply system. When it is desired toactuate the slave flash tube units the switch 31 is closed, shorting thewinding 15 and thereby interrupting or decreasing the oscillation of theLC circuit and discontinuing the transmission of the carrier signal orreducing it to an ineiiective value. The rectifier 30 demodulates theshorted signal and also acts to prevent radio-frequency radiation andattenuation in the line g0- ing to the switch 31.

The receiver circuit is shown in FIGURE 2 and includes a series resonantcircuit including a transformer Eli which may be a standard LP.transformer tuned with powdered core slugs adapted to receive 1'95 kc.plus or minus 4-6 kc. provided with pad capacitors 5i and 52 to time thewindings. A compensating capacitor 53 is used to adjust the circuit toreceive the 195 kc. carrier signal. The carrier current signal isrectified by a hi; ily conducting germanium diode providing negativebias for base 55 of a PNF-transistor having emitter 57 and a collector53. The negative bias received by the base of the transistor causes itto conduct and eifectivey to short out a resistor till connec ed betweenthe emitter 57 and the collector A decoupling capacitor 61 is connectedbetween the base 55 and the collector 5:3, the collector being groundedas indicated at-Z. A bias resistor as is connected from base 5d toconnecting wire 64 from end 65 of the transformer 55;, the other end 66of tr e transformer 5% being connected to the rectifier 54.

The receiver circuit is connected to a terminal board or connecting plug7% having connectors 712-76 thereon. Connector 72 is a supply lineterminal and is connected through an isolation capacitor 77 to terminal78 of th transformer 5 d. Connector '73 is another supply line terminaland is connected directly to terminal '7 of the transformer 5d.Connector 74 is a high voltage supply and is connected through a highvoltage isolating resistance $9 to connecting wire 64-. Connector is acontrol circuit and is connected through a zener diode S1 in series witha coupling capacitor 82 to the connecting wire Connector "id is a groundconnection.

The electronic flash unit is connected to a terminal board or connectingplug 7% having connectors thereon engaging the connectors 72-76 andnumbered the same for ease of understanding. The electronic flash unitis mainly conventional and includes a transformer 9b with a low voltageprimary winding 91 and a high voltage secondary winding 92 to step upthe 120 volt supply to 350 volts. End 93 of the high voltage Winding 92is grounded while end 34 is connected through a current limitingresistance 95 to a full wave voltage doubling capacitor bank includingrectifiers 96 and 97 and capacitors 98 and 99*. The output of thecapacitor bank, 1% and Trill, is connected to electrodes 1G2 and 103 ofa gas discharge lamp or flash tube 164.

A triggering circuit for the flash tube 164 includes a triggeringelectrode MS, a triggering transformer res and a triggering capacitorM7. The triggering circuit is c011- trolled by a thyratron 11d. Anode111 of the thyratron lllii connected through a resistance 112 to adirect current supply and to the triggering capacitor 107. Cathode 12 ofthe thyratron 116 is connected to ground and to a grid 121. Control grid122 of the thyratron 110 is connected to the connector 7 5 for operationfrom the receiver.

In the operation of the receiver the received carrier sigprovides anegative bias on the collector 55 of the transistor 56 and thuseflectively shorts out the resistor 66'. During the period while thecarrier signal is present the capacitor 32 is charged with its positivepolarity connected to connecting wire 64 thus there is a negative biason the grid r22 which prevents the thyratron from conducting and thetriggering transformer N7 is charged through the resistor $.12. Upon theclosing of the switch 31 the carrier signal is interrupted or decreasedat the receiver and the collector 55 of the transistor 55 loses itsnegative bias and thus the transistor ceases to short the resistance atCapacitor 82 then produces a positive pulse on the control grid 122 ofthe thyratron 110 which causes it to conduct thereby producing a pulsedischarge of the capacitor 167 through the triggering electrode lflSinitiating the discharge of the flash tube 104.

An electrical system manufactured commercially and found to operatesatisfactorily employs constants for the various circuit components asfollows:

Tube 10-32 ETS Sylvania. Transmitter oscillator coil l1modified standardmanufacture:

Winding i2800 turns. Winding l3100 turns. Winding l410 turns. Winding200 turns. Rectifier i6lN 1763 RCA. Capacitor 22-15O mmfd. Resistance2312K. Padder condenser 25-300 mmfd. Capacitor 2S2.0 mfd. Filtercapacitor 29-40 mfd. Rectifier 3t?lN 1763 RCA. Capacitor 33-01 mfd.Transformer Sil -standard 45 5 ltc. intermediate frequency. Capacitor53-.0()1 mfd. Diode Si t-IN 46A Sylvania. Transistor 562N 1193 Motorola.Resistance nth-100K Capacitor GEL-.001 mfd. Resistor 63-100K. Capacitor'77-5G0 mrnfd. Resistance 80-4 meg. Rectifier 8lRS6 Hoffman. Capacitor$2-.1 mfd. Tube lllil2D2l GE. Resistance 112-100K.

While the invention has been described and illustrated with reference toa specific embodiment thereof, it will be understood that otherembodiments may be resorted to without departing from the invention.Therefore, the form of the invention set out above should be consideredas illustrative and not as limiting the scope of the following claims.

I claim:

1. An electrical system for photographic flash units comprising a powersupply, a transmitter oscillator including a tank winding, an outputwinding, and a shorting winding coupled with the tank winding, acoupling capacitor connected in series with the output winding acrossthe power supply a rectifier, a normally open shorting switch connectedin series with the rectifier across the shorting winding operative todecrease the oscillations of the output winding, a receiver including atuned transformer connected to the power supply, "a receiver rectifierin the sec ondary output of the transformer to produce a negative bias,a transistor having a base, a collector and an emitter, a resistance,the base connected to the receiver rectiiier to normally receive anegative bias, the resistance connected across the collector and emitterso that the resistance is effectively shorted while the base isnegatively biased, a flash tube, a capacitive power supply for the flashtube, a triggering control for the flash tube including a triggeringcapacitor adapted to initiate discharge of the flash tube, means tocharge the triggering capacitor, normally non-conducting means connectedto the triggering capacitor, means to render said non-conductive meansconductive operative upon the shorting of said resistor by thetransistor, whereby the triggering capacitor is discharged to initiatedischarge of the flash tube.

2. An el ctrical system for photographic flash units comprising a powersupply, a transmitter oscillator including a tank winding, an outputwinding, and a shorting winding coupled with the tank winding, acoupling capacitor connected in series with the output winding acrossthe power supply, a rectifier, a normally open shorting switch connectedin series with the rectifier across the shorting winding operative todecrease the oscillations or the output winding, a receiver including atuned transform r connected to the power supply, a receiver rectifier inthe secondary output of the transformer to produce a negative bias, atransistor having a base, a collector and an emitter, a resistance, thebase connected to the receiver rectifier to normally receive a negativebias, the resistance connected across the collector and emitter so thatthe resistance is eiiectively shorted while the base is negativelybiased, a flash tube, a capacitive power supply for the flash tube, atriggering control for the flash tube including a triggering capacitoradapted to initiate discharge of the flash tube, means to charge thetriggering capacitor, 21 thyratron including a cathode, an anode and agrid, the anode connected to the triggering transformer, and the gridconnected to said resistor so that upon the shorting of the resistor thegrid causes the thyratron to become conductive, whereby the triggeringcapacitor is discharged to initiate discharge of the flash tube.

3. An electrical system for photographic flash units comprising a powersupply, a transmitter oscillator including a tank winding, an outputwinding, and a shorting winding coupled with the tank winding, couplingmeans connected in series with the output winding across the powersupply, a normally open shorting switch connected across the shortingwinding operative to decrease the oscillations of the output winding, areceiver including a tuned transformer connected to the power supply, areceiver rectifier in the secondary output of the transformer to producea negative bias, a transistor having a base, a collector and an emitter,a resistance, the base connected to the receiver rectifier to normallyreceive a negativebias, the resistance connected across the col lectorand emitter so that the resistance is effectively shorted while the baseis negatively biased, a flash tube, a capacitive power supply for theflash tube, a triggering control for the flash tube including atriggering capacitor adapted to intiate discharge of the flash tube,means to charge the triggering capacitor, normally non-conducting maensconnected to the triggering capacitor, means to render saidnon-conductive means conductive operative upon the shorting of saidresistor by the transistor, whereby the triggering capacitor isdischarged to initiate discharge of the flash tube.

4. An electrical system for photographic flash units comprising a powersupply, a transmitter oscillator in cluding a tank winding, an outputwinding, and a shorting winding coupled with the tank Winding, acoupling capacitor connected in series with the output winding acrossthe power supply, a rectifier, a normally open shorting switch connectedin series with the rectifer across the shorting winding operative todecrease the oscillations of the output winding, a receiver including atuned transformer connected to the power supply, a receiver rectifier inthe secondary output of the transformer to produce a bias, an electronicswitch responsive to the bias of the rectifier, the resistance connectedacross the electronic switch so that the resistance is effectivelyshorted while the electronic switch is biased, a flash tube, acapacitive power supply for the fiash tube, a triggering con- 10 trolfor the flash tube including a triggering capacitor adapted to initiatedischarge of the flash tube, means to charge the triggering capacitor,normally non-conducting means connected to the triggering capacitor,means to 6 render said non-conductive means conductive operative uponthe shorting of said resistor by the electronic switch, whereby thetriggering capacitor is discharged to initiate discharge of the flashtube.

References Cited in the file of this patent UNITED STATES PATENTS2,177,843 Seeley Oct. 31, 1939 2,358,796 Edgerton Sept. 26, 19442,378,326 Rees et al June 12, 1945 2,431,902 Albin Dec. 2, 19472,549,923 OBrien Apr. 24, 1951 2,624,831 Farber Jan. 6, 1953 2,802,938Herzog Aug. 13, 1957

1. AN ELECTRICAL SYSTEM FOR PHOTOGRAPHIC FLASH UNITS COMPRISING A POWERSUPPLY, A TRANSMITTER OSCILLATOR INCLUDING A TANK WINDING, AN OUTPUTWINDING, AND A SHORTING WINDING COUPLED WITH THE TANK WINDING, ACOUPLING CAPACITOR CONNECTED IN SERIES WITH THE OUTPUT WINDING ACROSSTHE POWER SUPPLY, A RECTIFIER, A NORMALLY OPEN SHORTING SWITCH CONNECTEDIN SERIES WITH THE RECTIFIER ACROSS THE SHORTING WINDING OPERATIVE TODECREASE THE OSCILLATIONS OF THE OUTPUT WINDING, A RECEIVER INCLUDING ATUNED TRANSFORMER CONNECTED TO THE POWER SUPPLY, A RECEIVER RECTIFIER INTHE SECONDARY OUTPUT OF THE TRANSFORMER TO PRODUCE A NEGATIVE BIAS, ATRANSISTOR HAVING A BASE, A COLLECTOR AND AN EMITTER, A RESISTANCE, THEBASE CONNECTED TO THE RECEIVER RECTIFIER TO NORMALLY RECEIVE A NEGATIVEBIAS, THE RESISTANCE CONNECTED ACROSS THE COLLECTOR AND EMITTER SO THATTHE RESISTANCE IS EFFECTIVELY SHORTED WHILE THE BASE IS NEGATIVELYBIASED, A FLASH TUBE, A CAPACITIVE POWER SUPPLY FOR THE FLASH TUBE, ATRIGGERING CONTROL FOR THE FLASH TUBE INCLUDING A TRIGGERING CAPACITORADAPTED TO INITIATE DISCHARGE OF THE FLASH TUBE, MEANS TO CHARGE THETRIGGERING CAPACITOR, NORMALLY NON-CONDUCTING MEANS CONNECTED TO THETRIGGERING CAPACITOR, MEANS TO RENDER SAID NON-CONDUCTIVE MEANSCONDUCTIVE OPERATIVELY UPON THE SHORTING OF SAID RESISTOR BY THETRANSISTOR, WHEREBY THE TRIGGERING CAPACITOR IS DISCHARGED TO INITIATEDISCHARGE OF THE FLASH TUBE.